Without wishing to bang on about it, I can't get my head around this view. We have photographs, physical evidence, witness accounts, and so on, of the holocaust. A historian should certainly learn that these things are the tools of a proper historian. When they learn about a historical event they should learn about the evidence that it happened. But having shown a student all these pieces of evidence that unerringly indicate that the holocaust did happen - only to say "but some people think it didn't" - surely that undermines the sceptical, scientific mindset that you want to encourage?

The fact is that you can't teach every crackpot theory there is. So there will always be ideas that people only encounter when they reach adulthood, and if they are sufficiently gullible, they will swallow whole, and spout such phrases as "there's a big conspiracy to hush it up". The only way to protect against this is to teach scepticism and scientific method - not to teach theories that are in fact discredited by these very methods.